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Muscle function in children
Insights
Muscle strength in children is primarily determined by muscle mass, not age or sex. Force-generating capacity and fatigue resistance of the triceps surae remain consistent from adolescence through early adulthood.
Area of Science:
- Physiology
- Biomechanics
- Pediatric Exercise Science
Background:
- Understanding the developmental trajectory of muscle contractile properties is crucial for pediatric sports science and rehabilitation.
- Previous research has established adult baseline data, necessitating comparative studies in pediatric populations.
Purpose of the Study:
- To compare the electrically evoked mechanical and contractile properties of the triceps surae in children and adults.
- To investigate the influence of age and sex on muscle strength and fatigue in adolescents.
Main Methods:
- Electrically evoked mechanical and contractile properties of the triceps surae were measured in 52 children (aged 11 and 14 years).
- Data were compared with previously published adult data.
- Muscle strength was assessed via tetanic tensions and maximal voluntary contraction (MVC), standardized for cross-sectional area (CSA).
Main Results:
- Twitch properties (time to peak tension, half relaxation time, supramaximal tension) were similar between sexes and independent of age in children.
- Older children (14 years) exhibited greater absolute strength than younger children, but both groups were weaker than adults.
- When standardized for calf muscle CSA, strength differences between children and adults disappeared.
- Force loss during fatigue testing was comparable between children and adults.
Conclusions:
- Absolute muscle strength differences in children are primarily attributed to variations in muscle mass.
- The intrinsic force-generating capacity (per unit CSA), fatiguability, and contraction/relaxation times of the triceps surae remain consistent throughout adolescence and into early adulthood.
Abstract:
Electrically evoked mechanical and contractile properties of the triceps surae have been measured in 52 children aged 11 and 14 years, and results compared with previously reported data for adults (Davies and White 1982). The results show that the time to peak tension (TPT), half relaxation time (1/2RT) and supramaximal tension (Pt) of the twitch were not significantly (P greater than 0.1) different in girls and boys and independent of age. The 14-year-old girls and boys were stronger in terms of their supramaximal 10, 20, and 50 Hz tetanic tensions and maximal voluntary contraction (MVC) than their younger counterparts, and both groups of children were significantly (P less than 0.001) weaker than the young adults. However, if standardisation was made for an anthropometric estimate of calf muscle (plus bone) cross-sectional area (CSA), the differences in strength disappeared. Electrically stimulated and voluntary maximal force per unit CSA measured at the knee were 17.1 and 20.5 N X cm2 respectively and independent of sex and age. The loss of force during a 2-min stimulated fatigue test was the same in the children as the adults. The average fatigue indices ranged from 0.52 to 0.72 in the children, compared with 0.68 in the adults. It is concluded that absolute differences in muscle strength in children are a function of muscle mass. The force generating capacity expressed in N X cm2, fatiguability, contraction and relaxation times of the triceps surae would appear to remain unchanged through adolescence and early adulthood.